Owlbear

Trample
Keen Senses — When Owlbear enters, draw a card.

Werebear

{T}: Add {G}.
Threshold — Werebear gets +3/+3 as long as seven or more cards are in your graveyard.

Realmwalker

Changeling (This card is every creature type.)
As Realmwalker enters, choose a creature type.
You may look at the top card of your library any time.
You may cast creature spells of the chosen type from the top of your library.

Grizzly Bears

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Runeclaw Bear

Sol Ring

Wilson, Refined Grizzly

This spell can't be countered.
Vigilance, reach, trample
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Choose a Background (You can have a Background as a second commander.)

Forest

Garruk, Primal Hunter

+1: Create a 3/3 green Beast creature token.
−3: Draw cards equal to the greatest power among creatures you control.
−6: Create a 6/6 green Wurm creature token for each land you control.

Ayula, Queen Among Bears

Whenever another Bear you control enters, choose one —
• Put two +1/+1 counters on target Bear.
• Target Bear you control fights target creature you don't control.

Mother Bear

{3}{G}{G}, Exile Mother Bear from your graveyard: Create two 2/2 green Bear creature tokens. Activate only as a sorcery.